In recent years, as it is urgently needed to reduce the uses of CO2, SO2 and NO2 which are the key factors to global warming, a new lighting development is inevitable, which might attract significant attention as a technology of a green growth helping significantly reduce power consumption and resource waste, maximize the efficiency of light source and embody the coexistence of green and growth.
LED (Light Emitting Diode) lighting using a LED has advantages in terms of both low power consumption and a semi-permanent environment and economic use. It is known to be environmentally friendly with the features that it has a long service life eight times longer than a neon fluorescent lighting, and it has a power consumption 67% lower than an incandescent lamp, and 17% lower than fluorescent lighting, and it uses a mercury free light source which is environmentally friendly; however there are still a lot of problems to be resolved, in view of the efficiencies of light emission.
LED lighting is generally made by binding one or multiple LED devices together which emit red, green and blue colors when electric power is applied to them. The light emitting principle of the LED was observed as light was emitted when applying electric power to a semiconductor in 1907. The electron (e) of the semiconductor has a certain deviation in energy as energy is externally supplied. At the moment electron changes from a higher energy to a lower energy, light emits. When the difference between energies is large, blue color light emits, when small, a red color light emits, and when middle, a green color light emits. The red color LED was for the first time commercialized by the US general electronic (GE) in 1962, and the blue color LED was developed by Shuji Nakamura of Nichia Corporation in 1993. The Nichia Corporation developed a white color LED which emitted a white color light in such a way to adapt a yellow color fluorescent substance to a blue color LED in 1997. Afterward, the LED can emit various colors by combining together red, green and blue colors, even white color. As the white color LED was developed, it became possible to set up a foundation for the purpose of producing a lamp which can substitute an ordinary lighting in the field of an electronic display product.
LED lighting, which uses a LED substituting an ordinary lighting, might be further intensively developed for a research and development for various applications with the aid of an original technology. In terms of the technology of the level of Lumen/Watt [Im/W] representing a light emitting efficiency of a high luminance LED, many leading companies are competitively developing products with the highest light source efficiencies. Nowadays, the US Cree company, the Germany Osram company and the Japan Nichia company account for almost the market shares as they produce most of the related products.
The high luminance power LED lighting produces 3.3V of VF voltage and 700 mA of IF current based on 3 W-level criteria; however it has a problem that a heat radiation of a high temperature heat at a backside of a power LED generating during a procedure that light emits as a large current is applied to a small LED device is hard, generating a big issue.
The power LED, which is a high output LED above 1 watt (W) is known to consume a lot of electric power, and since the current amount is large, a light emitting efficiency is high; however a heating level of a LED chip seems to be high, which needs a proper measurement, otherwise the temperature of a LED chip rises too high, thus degrading a chip itself or a packaging resin. Subsequently, a light emitting efficiency is lowered, for example luminance is lowered, and a service life of a chip is shortened. So, it is necessarily needed to develop a heat radiation technology so that a semi-permanent life span of a LED, which is one of the biggest features, cannot be degraded.
In order for a LED to be used for the purpose of a light source for lighting, a modulation technology of it is necessary needed, the key technology of which is related to a heat radiation design based on a package material. The heat radiation design technology is a key technology needed for the purpose of manufacturing a lighting product using a LED.
The power LED package, which is currently used, has a variety of kinds and is generally used for the purpose of a PCB (Printed Circuit Board) type and a horizontal type; however the common matters of them lie in that the volume increase since a high luminance power LED is used in a PCB state. Besides, there is a limit in increasing the output now that a lot of heat occurs as much as the consuming electric power since the consuming electric power is 0.5˜1 watt even though the size of the used chip is 20, 28, 40 mil ( 1/1000 inches).
The most important matter in terms of a power LED is the loss of a chip due to heat. The aging of the LED goes on fast due to the heat, and the luminance is lowered. In order to resolve the above mentioned problems, domestic and foreign related companies are competitively developing heat sinking planes and are also researching a method for a high efficiency with a lower electric current. Light energy is directed to a thing which emits light with heat itself, so it cannot emit light without generating heat. The important matter lies in that how much heat is actually converted into light energy in order to enhance the efficiency of products, which results in good competitiveness.
In other words, if a heating point temperature is maintained constantly by applying a VF voltage and an IF current to a power LED, the LED might be considered as the LED light source having the highest light emitting efficiency on the earth (refer to FIG. 1); however the problems in terms of the backside heat radiation process technology of the power LED basically remains unresolved, instead it is known to control somehow the heating in such a way that the light emitting efficiency of the power LED device is lowered 30˜40% by driving with the current of a tens mA by lowering the VF voltage and the IF current to a degree low enough not to turn off the device of the power LED or in such a way that the voltage is raised, fixing the current. In more details, if the voltage is 3 watt, the use of 700˜750 mA is normal; however the currently applied technology is directed to resolving the heat radiation problems by reducing the heat generation in such a way to lower the current as compared with the output by packaging in a form that the voltage is increased, and the current is fixed.
When using the power LED in a place where needs a large light source such as streetlights, security lamps, park lamps, tunnel lamps, factory lamps, plaza halo lamps, angling lamps, military lamps for special operations, search light lamps, etc., it is needed to upgrade the system efficiency of the LED device to 70˜85% by driving with a hundreds mA of current rather than to decrease the VF voltage and the IF current.
In Korea, a LED light source module for a white lighting of 2500 lumen/watt [Im/W] and a heat resistance 1 Kelvin/watt (K/W) has been developed, which can be adapted to a head light of a vehicle; however it needs 70 heat radiation chips for 0.95 K/W of a heat resistance for the sake of heat radiation process.
Since a relatively high heat generates at a heat radiation point of a heating portion of a backside of a power LED, the heat radiation process problem should be resolved, so it seems that only the high luminance power LED lighting appliances with a heat radiation process function can have competitiveness.